It is known that a boot can be retained in support on a ski by means of a front binding element and a rear binding element. Each retention element has a jaw that is borne by a body, which is movable against the return force exerted by an energizing spring, generally a compression spring.
The invention is more specifically related to a front binding element. Usually, the front binding element reacts to a lateral stress from the front end of the boot. Such a bias is a result of a pure torsional bias on the skier's leg. When the fall is complex, such an element reacts to the lateral component of the bias exerted by the boot.
In order to take into account the other bias components, especially the upward or downward vertical components, the binding elements are equipped, in addition, with compensation mechanisms. Thus, some binding elements react to an upward vertical bias. This type of bias means that the skier falls towards the back. European Patent Application No. 102,868 describes such a binding, for example.
Other bindings have a compensation mechanism that reacts in case of a torsional bias combined with a frontward fall of the skier. Such a mechanism is described, for example, in German Patent Application No. 2,905,837. Such a mechanism comprises a vertically movable support plate for the boot, whose movement caused by a downward vertical pressure of the boot reduces the return force that the spring exerts on the jaw.
Another mechanism is described in German Patent Application No. 3,335,878. This mechanism also comprises a support plate for the boot that is vertically movable and that forces the jaw to become displaced in the direction of the release of the boot.
Such devices compensate the increased friction of the boot on its supports that is induced by the frontward component of the fall. Such mechanisms are satisfactory as long as the lateral component of the fall remains preponderant with respect to the vertical component.
However, it is to be noted that in some so-called "pre-torsion" falls, i.e, having a frontward component as well as a lateral component, the lateral component is not enough to cause the lateral pivoting of the jaw. This results in the boot becoming twisted and stuck between the jaw and its support plate. Currently known compensation mechanisms are not active enough to cause the jaw to open. This results in dangerous falls and cause injuries, especially near the skier's knees.